filO,q/3Wl 


BULLETIN  No.  47 


Under  the  snperrision  of  the 
UNITED  STATES  DEPARTMENT  OP  AGRICULTURE 


J.  C.  RIPPERTON,  Chemist 


\S 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION 

HONOLULU,  HAWAII 


APPLICATION  OF  THE 

PRINCIPLES  OF  JELLY  xMAKING 

TO  HAWAIIAN  FRUITS 


BT 


Issued  Jane  21,  1*21 


HINGTON 
T  PRINTING  OFFICE 
1121 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION 

HONOLULU,  HAWAII 


BULLETIN  No.  47 


Under  the  supervision  of  the 
UNITED  STATES  DEPARTMENT  OF  AGRICULTURE 


APPLICATION  OF  THE 

PRINCIPLES  OF  JELLY  MAKING 

TO  HAWAIIAN  FRUITS 


BY 


J.  C.  RIPPERTON,  Chemist 


Issued  June  21,  1923 


WASHINGTON 
GOVERNMENT   PRINTING   OFFICE 

1923 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION,  HONOLULU. 

[Under  the  supervision  of  the  States  Relations  Service,  United  States  Department  of  Agriculture.l 

A.  C.  True,  Director. 

E.  W.  Allen,  Chief,  Office  of  Experiment  Stations. 
Walter  H.  Evans,   Chief,  Division  of  Insular  Stations,  Office  of 
Experiment  Stations. 

STAFF. 

J.  M.  Westgate,  Agronomist  in  Charge. 

H.  L.  Chung,  Specialist  in  Tropical  Agronomy. 

W.  T.  Pope,  Horticulturist. 

J.  C.  Ripperton,  Chemist. 

R.  A.  Goff,  In  Charge  of  Glenwood  Substation  and  Extension  Agent. 

for  Island  of  Hawaii. 
Nellie  A.  Russell,  Collaborator  in  Home  Economics. 

II 


APPLICATION  OF  THE  PRINCIPLES  OF  JELLY 
MAKING  TO  HAWAIIAN  FRUITS. 


CONTENTS. 


Page. 

Introduction 1 

Methods 1 

The  guava  for  jelly  making 4 

Effect  of  varying  proportions  of  sugar,  pec- 
tin, and  acid  in  jelly  making 9 


Page. 

Other  Hawaiian  fruits  for  jelly  making 14 

Consistency  of  jellies  as  affected  by  the  physi- 
cal properties  of  pectin 22 

Summary 23 


INTRODUCTION. 

Although  tropical  fruit  products  have  been  given  wide  publicity 
within  recent  years  and  there  is  an  ever-increasing  demand  for  them 
on  the  world  markets,  jelly  making  from  tropical  fruits  remains  as 
yet  a  comparatively  undeveloped  industry.  Probably  the  only 
two  tropical  fruit  jellies  of  any  commercial  importance  at  the  present 
time  are  those  made  from  guava  (Psidium  guayava)  and  poha  (Physalis 
peruviana).  Guava  jelly,  owing  to  the  comparatively  small  cost  of 
production  and  the  growing  of  the  wild  fruit  in  abundance,  is  the 
standard  jelly  as  well  as  the  basic  product  of  the  fruit  jelly  industry 
in  Hawaii.  Poha  jelly  production  is  as  yet  small,  owing  to  the 
limited  supply  and  high  cost  of  the  fniit.  Since  the  exportation 
in  the  fresh  state  of  many  Hawaiian  fruits  is  prohibited  by  quarantine 
regulations,  the  fruit  jelly-making  industry  in  Hawaii  should  serve 
as  a  stimulus  for  producing  and  exporting  Hawaiian  fruit  products 
in  greater  abundance  than  is  now  the  case. 

Extensive  studies  have  been  made  of,  and  formulae  developed  for, 
the  making  of  jellies  from  every  important  fruit  of  the  Temperate 
Zone,  but  little  or  no  study  has  been  devoted  to  the  making  of  jelly 
from  fruits  from  the  Tropics.  The  writer,  therefore,  made  an  ex- 
haustive study  of  the  Hawaiian  guava  for  jelly  making  for  the 
purpose  of  developing  a  systematic  procedure  by  means  of  which 
jelly  may  successfully  be  made  from  any  kind  of  jelly  fruit.1  This 
ulletin  gives  the  results  of  the  investigation. 

METHODS. 

A  review  of  the  different  studies  on  jelly  making  showed  that 
there  are  no  generally  accepted  methods  for  conducting  a  systematic 
study  of  the  jelly-making  qualities  of  a  fruit,  and  that  the  tendency 
is  to  develop  formulae  for  different  fruits  rather  than  general  prin- 
ciples which  will  apply  to  all  jelly  fruits.  The  methods  followed 
by  the  writer  require  little  time  and  simple  apparatus,  and  while 
the  results  obtained  from  their  use  can  not  be  considered  in  the 
light  of  accurate  quantitative  results,  they  are,  it  is  thought,  suffi- 
ciently accurate  for  a  practical  study  of  jelly  making. 

1  A  fruit  containing  the  essential  constituents  for  jellying,  i.  e.,  pectin  and  acid. 


i6 


2  BULLETIN    47,    HAWAII   EXPERIMENT    STATION. 

DETERMINATION  OF  PECTIN  IN  FRUIT  JUICES. 

Careful  search  through  literature  failed  to  give  any  quick,  prac- 
tical method  for  determining  the  pectin  content  of  fruit  juices.  As 
a  rule  the  pectin  content  is  not  determined,  and  the  quantity  present 
is  indicated  by  specific  gravity  or  by  means  of  the  Brix  hydrometer. 

The  Brix  reading  indicates  at  once  the  proportion  of  sugar  that 
should  be  added  to  the  juice  in  accordance  with  tables  that  have 
been  worked  out  for  apple  juice,  but  since  such  tables  are  of  no 
value  in  connection  with  other  fruits  a  separate  table  must  be  con- 
structed for  each  specific  fruit. 

Home  economics  text  and  cook  books  commonly  advocate  the 
method  of  adding  fruit  juice  to  alcohol  in  a  tumbler  to  determine 
the  pectin  content  of  a  juice.  The  appearance  of  the  precipitated 
pectin  when  poured  out  is  taken  as  an  indication  of  the  content, 
the  juice  being  said  to  contain  a  high  percentage  of  pectin  when 
the  precipitate  pours  out  in  a  single  lump,  only  a  medium  quantity 
when  there  are  several  small  lumps,  and  not  enough  pectin  for 
jelly  making  when  there  are  no  lumps.  Many  substances,  such  as 
magnesium  sulphate,  can  be  used  in  place  of  alcohol  to  precipitate 
the  pectin.  This  method,  while  valuable  for  the  housewife,  was  not 
deemed  sufficiently  accurate  to  be  of  use  in  connection  with  the 
present  investigation. 

Quantitative  methods  entailing  precipitation,  filtration,  weighing,, 
and  ignition  require  too  much  time  for  completion  to  be  of  practical 
use  in  jelly  making. 

By  means  of  a  cylinder,  graduated  to  25  cubic  centimeters  and 
fitted  with  a  plunger,2  a  pipette,  to  deliver  the  juice  to  the  alcohol 
drop  by  drop,  and  a  piece  of  silk  bolting  cloth  about  4  inches  square,, 
the  writer  developed  a  method  for  determining  the  pectin  content 
of  fruit  juices.  (PI.  I,  Fig.  1.)  After  20  cubic  centimeters  of  95  per 
cent  ethyl  alcohol  were  measured  into  tha  cylinder,  10  cubic  centi- 
meters of  the  juice  to  be  tested  were  added  drop  by  drop  to  the 
alcohol.  The  contents  of  the  cylinder  was  then  filtered  through  the 
silk  bolting  cloth,  which  was  rolled  back  and  forth  in  the  hand 
until  the  pectin  precipitate  gathered  into  a  compact  mass  and  the 
alcohol  ceased  to  run  out.3  As  soon  as  the  pectin  mass  had  been 
rolled  into  cylindrical  shape  it  was  slipped  into  the  cylinder  and 
shaken  to  the  bottom.  The  plunger  was  then  placed  on  top  of  the 
mass  and  the  volume  in  cubic  centimeters,  or  "  pectin  number,"  was 
noted.  The  operation  required  only  three  to  five  minutes  with  most 
of  the  juices  tested,  and  duplicate  results  were  had  within  a  quarter 
of  a  cubic  centimeter. 

The  amount  of  alcohol  which  the  pectin  mass  will  retain  depends 
of  course  on  the  pressure  exerted.  The  purpose  of  rolling  on  the 
silk  cloth  is  to  remove  the  excess  alcohol  with  no  pressure  at  all 
other  than  that  exerted  by  its  own  weight.  The  purpose  of  the 
plunger  is  not  to  exert  pressure,  but  to  make  possible  an  accurate 
reading  of  the  pectin  number. 

The  relationship  existing  between  the  "pectin  number"  and  the 
percentage  of  pectin  was  determined  by  ascertaining  the  alcohol 
precipitate,  that  is,  the  impure  peetin,  for  which  purpose  the  method 

2  A  Nessler  tube  having  the  proper  diameter  can  be  used  as  the  plunger. 

3  In  this  operation  time'ean  be  saved  by  placing  the  cloth  upon  a  folded  towel  to  absorb  the  alcohol,  but, 
the  results  obtained  are  not  nearly  so  accurate  as  when  no  towel  is  used. 


JELLY   MAKING   WITH   HAWAIIAN   FRUITS.  6 

followed  by  the  Association  of  Official  Agricultural  Chemists  was 
used.4 

Table  1  gives  the  'pectin  number"  and  percentage,  as  well  as  the 
Brix  hydrometer  reading  of  several  guava  juices  and  of  one  juice 
each  of  the  poha.  grape,  and  roselle. 

Table  1. — Comparison  of  "pectin  number"  and  pectin  per  cent  in  fruit  juices. 


Frui-  juice. 

Pectin. 

b 

Brix 
reading. 

Character  of  precipitate. 

a 
a                b 

Guava 

Number.    Per  cent. 

3i           0. 446           0. 137 
4}             .578             .  136 
H             • 794             . 151 
S\            .963            .148 
1\            1.  141              .  157 
9|           1.661             .180 
•1\             .  431             .  172 
4"             .888            .223 

Degrees. 
3.6 

5.2 

J:  J 

9.6 
15.  4 
12. 6 

3.8 

Spongv  with  medium  Long  fibers. 
Do 

Do 

Do.i. 

Do 

Do 

Do 

Do 

Do. 

Do 

Do. 

Poha 

Dense  with  long,  tough  fibers. 

Grape...   . 

Roselle 

5J             .  977             .  186 

Spongy  with  short  fibers. 

1  Average. 


b   . 


Table  1  shows  that  the  factor  -  is  fairly  constant  for  guava  juice. 

a 

Any  increase  in  this  factor  for  juices  having  a  higher  pectin  content 

is,  of  course,  due  to  the  increased  pressure  exerted  by  the  greater 

bulk  of  precipitate  and  the  resultant  smaller  proportion  of  alcohol 

remaining  in  the  mass.     Guava  juices,  however,  seldom  contain  a 

pectin  number  greater  than  7^  or  less  than  3,  and  the  factors  within 

this  limit  vary  only  little. 

The  factors  for  the  juices  of  different  fruits  vary  considerably. 
This  variation  is  directly  traceable  to  the  character  of  the  precipitate 
because  the  swelling  power  of  the  precipitate,  or  its  capacity  to  absorb 
alcohol,  varies  with  the  character  of  the  pectin. 

The  Brix  reading  of  a  juice,  as  an  indication  of  the  pectin  content, 
is  unreliable,  unless  only  one  fruit  is  used  in  the  experiment.  The 
percentage  of  pectin  in  a  juice  may  be  computed  by  multiplying  its 

pectin  number  by  the  factor  -•     This  method  of  computation  was 

used  throughout  the  investigation.5 

PROPORTION  OF  SUGAR  TO  JUICE. 

The  following  method  was  used  for  systematically  determining  the 
best  proportion  of  sugar  to  add  to  the  fruit  juice. 

A  series  of  jellies  was  made  with  varying  quantities  of  sugar  to  1 
cupful6  of  juice,  a  start  being  made  with  three-quarters  of  a  cupful 
of  sugar  to  1  cupful  of  juice.  The  quantity  of  sugar  was  increased  a 
quarter  of  a  cup  at  a  time  until  a  sirup  or  gummy  mass  instead  of  a 


*  Methods  of  Analysis  of  the  Association  of  Official  Agricultural  Chemists.  Revised  to  Nov.  1,  191'.) 
Washington,  D.  C.  1920.  p.  1-56. 

*  For  use  of  the  "pectin  number"  method  in  investigational  work,  each  worker  should  determine  the 

factor  -  for  himself  so  as  to  eliminate  eventually  the  personal  factor.    For  practical  work,  however. 

variations  due  to  this  cause  are  negligible. 

6  Wherever  the  term  '•cupful"  is  used  in  connection  with  measurements  of  juice  and  sugar,  24o  cubic 
centimeters  of  juice  and  200  grams  of  granulated  sugar  are  taken  as  the  equivalent.  The  actual  volume  of 
a  half-pint  cup  is  235.6  cubic  centimeters.  However,  the  value  assumed  is  believed  to  be  nearer  the  actual 
measurements,  made  by  the  average  jelly  maker,  than  the  true  value. 


4  BULLETIN  47,   HAWAII  EXPERIMENT  STATION. 

jelly  resulted.  The  resultant  " jelly  series"  was  then  studied  to 
determine  the  relative  merits  of  each  of  the  different  proportions  of 
sugar  to  juice.  Each  member  of  the  series  was  brought  up  to  as 
standard  a  consistency  as  possible. 

CHEMICAL  ANALYSIS  OF  JUICES  AND  JELLIES. 

The  methods  of  analysis  recommended  by  the  Association  of  Official 
Agricultural  Chemists7  were  employed  in  making  analyses  of  the 
juices  and  jellies.  Sucrose  was  determined  by  polarization  before 
and  after  inversion  with  hydrochloric  acid,  reducing  sugar,  by  the 
volumetric  Fehling-solution  method  of  Munson  and  Walker,  and  crude 
pectin,  by  the  alcohol  precipitate  method.  The  acidity  was  then 
determined  by  titrating  with  fifth-normal  sodium  hydroxid,  with 
phenolphthalein  as  indicator.  Phenolphthalein  sufficed  for  work 
of  a  practical  nature,  even  with  the  highly  colored  juices  studied, 
since  the  natural  color  of  the  juice  faded  somewhat,  usually  changing 
to  pale  green,  before  the  end  point  with  the  indicator  was  reached 
and  the  color  change  of  the  latter  was  therefore  readily  discernible. 

THE  GUAVA  FOR  JELLY  MAKING. 

The  common  guava,  which  is  used  for  jelly  making,  is  a  conspicuous 
part  of  the  native  vegetation  of  Hawaii.  It  grows  over  wide  ranges 
of  altitude  and  rainfall  and  on  both  the  windward  and  the  leeward 
sides  of  all  the  islands.  The  ripe  fruit  can  be  obtained  the  year 
round,  but  the  main  crop  is  produced  from  June  to  October. 

Although  many  of  the  large  guava-producing  areas  are  leased  by 
commercial  jelly  companies,  large  numbers  of  guava  shrubs  are  to  be 
found  growing  along  highways  and  on  public  lands  where  the  fruit 
can  be  had  for  the  picking.  It  is  seldom  found  for  sale  on  any  of  the 
markets,  and  the  average  housewife  picks  her  guavas  from  whatever 
source  she  can  obtain  them.  Probably  the  only  well-established 
rule  governing  the  selection  of  guavas  in  Hawaii  is  that  fruit  from 
the  windward  side  of  the  island  is  inferior  for  jelly  making  to  that  on 
the  leeward  side. 

COMPOSITION  OF  GUAVA  JUICE. 

To  determine  the  composition  of  the  juice  of  an  average  guava  for 
jelly-making  purposes,  5  pounds  of  medium  ripe  guavas  was  cooked 
in  2.5  pounds  of  water  for  one  hour  and  then  allowed  to  drain  over- 
night. When  it  was  analyzed,  the  juice  was  found  to  have  the  fol- 
lowing composition: 


Table  2.- 

-Composition  of  guava  juice.a 

Constituent. 

Propor- 
tion. 

Constituent. 

Propor- 
tion. 

Sucrose 

Per  cent. 
1.04 
4.18 

Per  cent. 
0.96 

Reducing  sugars 

Acidity  (as  H2SO4) 

1.16 

a  Volume  of  drained  juice,  1,200  cubic  centimeters;  Brix  reading,  7.8. 

The  production  of  jelly  from  the  juice  of  the  guava  is  usually  con- 
sidered an  easy  task.  Experienced  jelly  makers,  however,  frequently 
have  difficulty  in  getting  a  firm  consistency,  and  jelly  factories  in 
producing  a  uniform  quality  of  jelly  from  guavas   that  have  been 

1  Methods  of  Analysis  of  the  Association  of  Official  Agricultural  Chemists.    Revised  to  Nov.  1, 191S 
Washington,  D.  C,  1920,  p.  153. 


JELLY   MAKING  WITH   HAWAIIAN   FRUITS.  0 

obtained  from  different  localities.  These  differences  have  been 
attributed  to  variations  in  the  composition  of  the  guava  juices,  which 
variations  in  turn  were  thought  to  be  due  to  the  widely  differing  locali- 
ties and  seasons,  as  well  as  to  varietal  differences,  individual  varia- 
tions in  the  same  variety,  and  varying  stages  of  maturity  of  the  fruit 
when  it  was  used. 

Variations  due  to  widely  differing  localities  and  seasons. — To  deter- 
mine the  effect  of  localities  and  seasons  upon  the  jelly-making  qualities 
of  the  juices,  three  guava-producing  areas,  representing  widely 
differing  conditions  of  climate,  altitude,  and  season,  were  selected 
for  study.  Guavas  from  each  of  the  areas  were  obtained  from  time 
to  time  and  their  juices  were  partially  analyzed. 

A  uniform  procedure  was  maintained  throughout  the  experiment. 
In  each  test  5  pounds  of  medium  ripe  guavas  were  cooked  with  2.5 
pounds  of  water  in  an  uncovered  2-gallon  granite-ware  container. 
After  the  mass  had  been  constantly  stirred  to  prevent  it  from  sticking 
to  the  container  and  gently  boiled  for  an  hour  to  effect  complete 
dissolution  of  the  partly  ripe  fruit,  it  was  allowed  to  drain  overnight 
in  a  double  cheesecloth  ba°:.  Only  the  juice  which  drained  through 
without  pressure  was  used  in  the  experiment. 

The  moisture  content  of  the  fruit  was  determined  by  drying  a 
pulped  sample  to  constant  weight  at  100°  C.  Only  the  Brix  corrected 
figures,  pectin  number,  and  acidity  of  the  juices  were  determined, 
since  the  pectin  and  acid  content  are  the  only  essential  constituents 
for  jelly  making.  The  variations  in  the  sugar  content  of  the  juice 
of  a  fruit  are  generally  too  slight  to  be  of  importance  in  this  connection. 

Table  3  gives  the  effect  of  localities  and  seasons  on  the  composition 
of  guava  juices. 

Table  3. —  Variations  in  the  composition  of  guava  juices  due  to  location  and  season. 


Location. 


Oct. 


Windward  Oahu:1 

Kailua 

Do 

Do 

Leeward  Oahu:3 

Manoa :  Sept. 

Do !  Sept. 

Do j  Sept.  22',  1921 

Do Nov.    8,1921 

Pa'olo I  Sept.    8,1921 

Manoa :  Feb.    2,1922 

Mountain  slopes:  * 

Tantalus Sept. 


Aug.  22,1921 
Sept.  19, 1921 
4, 1921 


8, 1921 
16. 1921 


Do. 
Do. 
Do. 


Jan. 
Jan. 
Feb. 


12. 1921 

11. 1922 
27,1922 

3,1922 


Moisture 

in 
guava. 


Per  cent. 
81.8 
85.3 

82.6 

86.  5 
83.3 
82.3 


83.6 
87.8 
87.0 
87.5 


Juice. 


Drained 
juice. 


Brix 
reading. 


Pectin 
No. 


Aciditv 
(asHtSOO 


Cubic 
centimeters. 
1,110 
1,180  | 
1,100  ! 

1,130  I 

1,180  j 

1,185 

1,200 

1,490 

1,205 

1,150 
1,415 
1,200 
1,210 


Degrees. 
8,7 
8,0 
9.4 

8.1 

8,3 
8,1 
8.7 
6.9 
7.0 

9.2 
8.4 
7.7 
7.4 


8! 

H 

'I 


Per  cent. 
0.99 
1.10 
.82 

1.50 
1.58 
1.66 
1.32 
1.39 
1.61 

1.24 
1.09 
1.16 
1.46 


1  The  guavas  from  Kailua,  Manoa,  and  Palolo  were  composite  samples  that  were  taken  from  ton  lots  of 
the  fruit.    Those  from  Tantalus  were  picked  from  only  a  few  trees  each  time. 
*  Elevation  100  feet, 
s  Elevation  300  feet. 
«  Elevation  1,500  feet. 

Table  3  shows  that  location  has  a  very  marked  effect  on  the  acidity 
of  the  juices  of  the  guava.  The  proportion  of  acidity  in  the  juices  of 
guavas  from  the  windward  side  of  Oahu  was  less  than  1  per  cent, 
while  in  fruits  from  the  leeward  side  it  averaged  nearly  1.5  per  cent. 
The  pectin  content  was  highest  in  fruit  from  the  windward  side  and 
lowest   in   that  from  the  mountain  slopes,  but  it  was  sufficiently 


6 


BULLETIN   47,    HAWAII   EXPERIMENT   STATION. 


high  in  all  instances  for  jelly  making.  The  superiority  for  jelly  making 
of  guavas  from  the  leeward  side  over  those  from  the  windward  slopes 
is  undoubtedly  due  to  the  high  acidity  of  the  former. 

The  variations  due  to  seasons  are  not  outstanding,  but  copious 
rainfall  during  the  winter  months  increases  the  percentage  of  water 
and  decreases  the  pectin  content  in  the  guava.        t 

Variations  due  to  varietal  differences. — Thompson8  gives  analyses 
of  six  different  varieties  of  guavas  in  Hawaii,  one  of  which,  the  straw- 
berry guava,  was  found  to  contain  more  acid  than  the  other  varieties, 
although  it  is  less  acid  to  the  taste.  The  only  guava  which  grows  in 
sufficient  quantity  to  be  of  practical  importance  for  jelly  making  is 
the  common  guava,  but  for  the  sake  of  comparison  the  juices  of  three 
other  varieties  of  guavas  were  tested.  The  results  of  the  test  are 
given  in  Table  4. 

Table  4. — Compisition  of  juices  from  different  varieties  of  guava. 


Moisture 

in 
guava. 

Drained 
juice. 

Juice. 

Variety. 

Brix 
reading. 

Sucrose. 

Reducing 

sugars. 

Pectin 

No. 

Acidity 
(asH;S04). 

Sweet  guava l 

Per  cent. 
87.1 
84.6 

Cubic 
centimeters. 
1,100 
1,190 
1.160 
1,200 

Degrees. 
5.8 
10.5 

Per  cent. 
0.22 

Per  cent. 
4.66 

5* 

7 

Ik 

6$ 

Per  cent. 
0.31 

1.65 

White  guava l 

10.3 

7.8 

1.99 

Common  guava 1 

87.5 

1.04 

4.18 

1.16 

i  Psidium  guayava. 


2  P.  cattle  ianum. 


It  is  apparent  from  Table  4  that  all  of  the  varieties  of  guava  tested 
contain  sufficient  pectin  for  jelly  making,  and  that  all,  with  the 
exception  of  the  sweet  guava,  have  sufficient  acid  for  jelly  making. 

Variations  due  to  individual  differences  in  the  same  variety. — The 
fruit  from  five  guava  bushes  was  kept  in  separate  containers  and  their 
juices  were  compared.  The  bushes  apparently  were  all  of  the  com- 
mon guava  variety  and  grew  in  the  same  locality.  The  fruits  selected 
from  them  were  as  near  the  same  degree  of  ripeness  as  it  was  possible 
to  select  them.  Table  5  gives  the  composition  of  the  juices  of  the 
fruits  from  five  trees. 

Table  5. — Composition  of  guava  juices  from  the  fruits  of  five  trees  growing  in  the  same 

locality. 


No.  of 
juice. 

Drained 
juice. 

Brix 
reading. 

Pectin 
No. 

Acidity 

(as 
H2SO4). 

No.  of 
juice. 

Drained 
juice. 

Brix 

reading. 

Pectin 

No. 

Acidity 

(as 
H2SO4). 

1 

2 

Cubic 
centi- 
meters. 
1,040 
1,050 

Degrees. 
9.9 
9.2 

8.4 

7* 

Per  cent. 
2.19 
1.16 

4 

5 

Cubic 
centi- 
meters. 
1 ,  235 
1,100 

Degrees. 

8.4 
8.0 

8 

n 

Per  cent. 
2.06 
.73 

3 

1,240 

7J 

1.09 

Table  5  shows  striking  variation  in  the  acidity  of  the  fruits,  but 
uniformity  in  pectin  content. 

Individual  variations  have  but  little  effect  where  the  fruit  is  picked 
in  ton  lots.  Variations  in  acidity  would  probably  be  rather  large 
where  the  fruit  is  gathered  from  only  a  few  bushes.  Uniformity  in 
acidity  results  when  the  fruits  are  picked  from  a  large  number  of 
bushes. 


*  Hawaii  Sta.  Rpt.  1914,  pp.  64,  67. 


JELLY   MAKING   WITH    HAWAIIAN   FRUITS. 


Variations  due  to  picking  at  different  stages  of  maturity. — Two  lots 
of  guavas  were  subdivided  according  to  their  stage  of  maturity  and 
the  juice  of  each  subdivision  was  analyzed.  The  composition  of  the 
juices  is  shown  in  Table  6. 


Table  6.- 


Composition  of  the  juices  of  guavas  which  were  used  at  different  stages  of 
maturity. 


Location. 

Stage  of  ripeness. 

Drained 
juice. 

Brix 

reading. 

Pectin 
No. 

Acidity 

(as 
H2S04). 

Total 
pectin 
ex- 
tracted.1 

Total  acid 
extracted 

(as 
H2S04). 

Manoa: 

Cubic 
centi- 
meters. 
1,365 
1,185 
815 

1,585 
900 

Degrees. 
8.5 
8.1 
9.4 

7.1 

8.5 

P 

10 

71 

8J 

Per  cent. 
1.39 
1.66 

2.55 

1.22 
1.95 

Grams. 
15.5 
14.8 
12.3 

18.6 
11.5 

Orams. 
18.97 

Lotl...; 

B;  full  yellow;  not  soft 

C;  greenish   yellow,   rather 

firm. 
[A;  quite  soft 

19.67 
20.78 

19.34 

Lot  2...j 

C;  greenish   yellow;   rather 
firm. 

17.55 

1  Pectin  numberX0.151X  cubic  centimeters  of  drained  juice  divided  by  100. 

From  Table  6  it  is  apparent  that  (1)  the  quantity  of  juice  increases 
as  the  fruit  matures;  (2)  the  pectin  content  of  the  juice  decreases 
with  increasing  maturity,  while  the  total  quantity  extracted  increases; 
and  (3)  the  proportion  of  acidity  decreases  very  rapidly  with  increas- 
ing maturity.  The  total  quantity  extracted  decreases  slightly  with 
increasing  maturity  in  fruit  of  the  lot  1  type  and  increases  in  fruit  of 
the  lot  2  type. 

These  experiments  have  demonstrated  that  the  pectin  content  in 
guava  fruit  is  iiniformly  high  under  all  conditions,  and  that  the  acid- 
ity is  subject  to  wide  variations.  Only  the  sourest  guavas  possible, 
with  a  good  proportion  of  half -ripe  fruit,  should  be  selected  for  jelly 
making,  because  juices  of  low  acidity  produce  jellies  of  inferior 
quality. 

PROPORTION  OF  WATER  TO  FRUIT  FOR  GUAVA  JELLY. 

To  5-pound  lots  of  fruit  varying  quantities  of  water  were  added  to 
determine  the  best  proportion  of  water  to  use  for  the  extraction  of 
juice.     The  results  of  the  experiment  are  given  in  Table  7. 


Table  7.- 


■Composition  of  guava  juices  obtained  by  using  various  proportions  of  water 
to  5-pound  lots  of  fruit. 


Pounds 
of  water 

to 
5-pound 
lots  of 
guavas. 


Location. 


2.5 
3.75 
2.5 
3.75  i 
5 

2.5  [ 
3.75  J 
5 


A,  Manoa. 

B,  Manoa. 

A,  Manoa . 

B,  Manoa. 

C,  Manoa . 

A,  Kailua. 

B,  Kailua. 

C,  Kailua . 


Drained 
juice. 


Cubic 
centi- 
meters. 
1,130 
1,850 
1,480 
1,985 
2,390 
1,005 
1,690 
2,110 


Juice. 


Brix 

reading. 


Degrees. 
8.1 
6.0 
7.1 
6.0 
5.5 
9.4 
6.5 
5.5 


Pectin 
No. 


Per  cent. 
1.50 
1.14 
1.51 
1.13 
1.03 
2.82 
.83 
.81 


Grams. 
13.2 
18.9 
15.6 
18.0 
20.7 
14.8 
18.5 
22.3 


Total  acid 
extracted 

(as 
H2SO4). 


Grams. 
16.95 
21.09 
22.34 
22.43 
24.62 
8.24 
14.03 
17.09 


Pectin  number  X0.151Xcubic  centimeters  drained  juice  divided  by  100. 

The  high  viscosity  of  this  juice  is  probably  the  cause  of  the  lack  of  concentration  of  acid . 

43822—23 2 


8 


BULLETIN  47,   HAWAII  EXPERIMENT  STATION. 


Table  7  shows  that  with  increasing  proportions  of  water  the  pectin 
number  decreases  but  the  total  pectin  extracted  increases.  The 
percentage  of  acidity  decreases  in  all  the  guava  fruit  except  the 
Kailua  guava,  and  the  total  acid  extracted  increases.  The  addition 
of  over  5  pounds  of  water  to  5  pounds  of  fruit  would  doubtless  in- 
crease the  total  extraction,  but  the  juice  would  be  diluted  to  such 
an  extent  that  prolonged  boiling  would  be  required  to  produce  a 
jelly.  When  the  cost  of  fruit  is  an  important  item  it  might  be  ad- 
visable to  use  a  greater  proportion  of  water  than  at  other  times,  but 
even  then  a  reboiling  of  the  pulp,  as  is  shown  in  the  following  para- 
graph, would  be  preferable. 

SECOND  EXTRACTION  OF  GUAVA  JUICE. 

The  guava  pulp  remaining  after  the  juice  is  drained  off  is  often 
thrown  away.  Guava  butter  can  be  made  from  the  pulp,  but  it  is 
never  as  much  in  demand  as  guava  jelly.  The  jelly  factories  have 
heretofore  treated  a  large  part  of  the  pulp  as  waste. 

To  determine  whether  a  second  cooking  would  produce  a  juice 
sufficiently  rich  in  pectin  and  acid  to  make  jelly,  the  pulp  which 
remained  after  the  first  juice  had  been  boiled  for  an  hour  and  then 
drained  was  reb oiled  with  water  for  30  minutes  and  allowed  to  drain 
overnight  in  a  cheesecloth  bag.  A  third  cooking  produced  a  muddy, 
dark-colored  juice  which  was  not  adapted  to  jelly  making.  Table  8 
gives  the  composition  of  the  juices  of  the  first  and  second  boilings  of 
two  lots  of  guavas. 


Table  8. — Composition  of  jh vices  from  guavas  which  v.ere  boiled  once  and  twice,  respectively. 

Juice 
No. 

Source  of  juice. 

Drained 

juice. 

Brix. 
.reading. 

Pectin 

No. 

Acidity 

(as 
HoS04). 

Total 
pectin 

ex- 
tracted.1 

Total  acid 
extracted 

(as 
H2SO4). 

A 

B 

c 

D 

5  pounds  of  fresh  Kailua  guava.. 
Pulp  from  AX1100  centimeters 

water 

5  pounds  of  fresh  Kailua  guava.. 
Pulp  from  CX1335  centimeters 

water 

Cubic 
centi- 
meters. 
1,100 

828 
890 

1,150 

Degrees. 

5.2 
9.2 

6.6 

1h 

7 

Per  cent. 

0.97 

.64 
1.04 

.66 

Grains. 
12.5 

S.  4 
11.1 

12.2 

Grams. 
10.67 

5.30 
9.26 

7.59 

1  Pectin  number  x0.15lxcubic  centimeters  drained  juice  divided  by  100. 

Table  8  shows  that  juice  resulting  from  the  second  extraction 
contains  almost  as  much  pectin,  but  not  nearly  so  high  a  proportion 
of  acidity,  as  does  the  juice  of  the  first  extraction. 

A  comparison  of  the  total  pectin  and  the  total  acid  contents  of 
A  and  B  with  those  of  C  and  D  shows  that  the  second  extraction 
contains  practically  as  much  total  pectin  and  acid  as  does  the  first 
extraction  when  the  latter  is  very  concentrated,  as  in  C;  and  that  the 
total  extraction  in  the  second  boiling  is  appreciably  less  when  the 
juice  of  the  first  extraction  is  sufficiently  dilute,  as  in  A. 

Jellies  of  good  quality  were  made  from  juices  of  the  second  ex- 
traction. As  a  rule  they  were  darker  in  tfolor  than  those  of  the  first 
extraction  and  did  not  possess  as  strong  a  guava  flavor.  Jelly  having 
as  high  a  sugar  ratio  as  the  juices  of  the  first  extraction  can  be  made 
when  sufficient  acid  is  added  to  the  juice  of  the  second  extraction. 

Second-extraction  guava  juice  is  now  being  used  by  the  various  jelly 
companies  of  Hawaii  to  meet  the  demand  for  a  low-priced  pure  fruit 
jelly.  The  only  cost  involved  in  producing  jelly  from  the  second- 
extraction  juice  lies  in  the  additional  30  minutes  required  for  boiling. 


Bui.  47,  Hawaii  Agr.  Expt.  Station. 


Plate  I. 


j"  ^^^Bl 

i 

*  g  - 

(us) 

** 

Fig.  I.— Determining  the  "  Pectin  Number"  of  a  Fruit  Juice 


Fig.  2.— Effect  of  Varying  Proportions  of  Sugar  (i  to   \\  Cups)  Upon 
the  Amount  of  Jelly  Produced  by  I  Cup  of  Fruit  Juice. 


JELLY   MAKING   WITH   HAWAIIAN   FRUITS. 


9 


EFFECT  OF  VARYING  PROPORTIONS  OF  SUGAR,  PECTIN,  AND  ACID  IN 

JELLY  MAKING. 

Considerable  difference  of  opinion  exists  among  investigators  as  to 
the  best  proportions  of  sugar,  pectin,  and  acid  to  use  in  making  jelly. 
X.  E.  Goldthwaite,9  working  with  a  wide  variety  of  fruits,  warns 
against  the  use  of  too  much  sugar.  She  considers  1  cupful  of  sugar 
to  1  cupful  of  juice  to  be  the  best  proportion  for  most  fruits.  Cruess 
and  McNair,10  dealing  with  a  number  of  California  fruits,  advocate 
the  use  of  1.5  pounds  or  more  of  sugar  to  1  pound  of  fruit  (equivalent 
1.75  cupfuls  of  sugar  to  1  cupful  of  juice).  They  found  that  jellies 
of  good  consistency  resulted  from  juices  containing  from  0.5  to  1.5 
per  cent  citric  acid  (equivalent  to  0.7  to  2  per  cent  sulphuric  acid), 
and  that  in  the  final  jelly  of  good  consistency  the  range  of  citric  acid 
varied  from  0.3  to  1.9  per  cent  (equivalent  to  0.4  to  2.7  per  cent 
sulphuric  acid). 

Goldthwaite,11  working  with  the  apple,  pear,  peach,  and  grape, 
concluded  that  an  acidity  greater  than  0.5  per  cent  of  the  juice  im- 
paired the  quality  of  the  jelly.  Later  on,  she  obtained  excellent 
jellies  from  currant  and  red  raspberry  juices  having  an  acidity  of 
2.417  and  1&09  per  cent,  respectively.  Campbell 12  found  that  apple 
juice  having  a  pectin  content  of  1.25  per  cent  was  necessary  to  pro- 
duce a  good  commercial  jelly,  and  that  only  0.75  to  1  per  cent  was 
necessary  to  produce  a  jelly  of  delicate  quality  for  household  pur- 
poses. Barker,13  working  with  apple  cider,  found  that  a  satisfac- 
tory apple  jelly  could  be  made  from  juice  containing  0.5  per  cent  of 


1  per  cent  or  more  of  pectin. 


is  evident  that  the  proportions  of  sugar,  pectin,  and  acid  can 
be  varied  within  rather  wide  limits  in  jelly  making,  not  only  with 
different  fruits  but  also  with  a  single  fruit. 


VARIATION  IN  SUGAR. 

Table  9  gives  the  results  of  tests  with  a  jelly  series  M  obtained  by 
the  addition  of  sugar  in  varying  proportions  to  a  constant  proportion 
of  juice  from  the  common  guava  (PL  I,  Fig.  2). 

Table  9. — Results  of  using  varying  proportions  of  sugar  with  a  constant  proportion  of 

juice  from  common  guavas.a 


Sugar 
ratio.  & 


Weight 
of  jelly. 


Grams. 
269 
341 
398 
446 

512 
584 


Propor- 

Specific 

Boiling 

tion  of 

gravity 

tempera- 

sugar. 

80°  C 

ture. 

Per  cent. 

°  C. 

55.  7 

1.27 

102.5 

5-.  7 

1.28 

103.  5 

62.8 

1.28 

104.0 

67.3 

1.29 

104.7 

68.5 

1.30 

105.0 

70.9 

l.*l 

106.0 

Consistency. 


Taste. 


Somewhat  tough 

Good:  a  trifle  tough 

Excellent 

Excellent;  somewhat  mel- 
low. 

Excellent;  mellow Very  mild;  sweet 

Poor— gummy Too  sweet . 


Rather  tart  and  strong  flavored. 
Tart:  rather  strong  flavored. 
Excellent. 
Excellent;  mild. 


«•  Analysis  of  juice:  Brix  reading.  8.1;  pectin  number,  7£;  acidity  (as  H2SO4),  1.19  per  cent. 

b  In  all  of  this  work  the  term  "  sugar  ratio"  signifies  the  cupfuls  of  sugar  added  to  1  cupful  of  juice. 

9  /our.  Indus,  and  Engin.  Chem.,  1  (1909).  No.  6,  p.  333. 
!<>  Jour.  Indus,  and  Engin.  Chem.,  S  (1916),  No.  5.  p.  417. 
11  Jour.  Indus,  and  Engin.  Chem.,  2  (1910).  No.  11,  p.  457. 
»  Jour.  Indus,  and  Engin.  Chem.,  12  (1920),  No.  6.  p.  568. 
13  Jour.  Soc.  Chem.  Indus.,  37  (1918).  No.  14.  p.  245. 
M  The  procedure  for  obtaining  a  jelly  series  is  given  on  p.  3. 


10 


BULLETIN  47,   HAWAII  EXPERIMENT  STATION. 


Table  10  gives  the  results  of  tests  with  a  jelly  series  obtained  by 
the  addition  of  sugar  in  varying  proportions  to  a  constant  proportion 
of  juice  from  the  strawberry  guava. 

Table  10. — Results  of  using  varying  proportions  of  sugar  with  a  constant  proportion  of 
juice  from  the  strawberry  guava.1 


Sugar    Weight 
ratio,    of  jelly. 


Grams. 
244 


376 
445 


Per  cent. 
61.5 
65.3 
66.5 
67.4 
74.8 


Specific  Boiling 
gravity  temper- 
S0°C.      ature.  i 


Consistency.2 


1.28 
1.30 
1.30 
1.30 
1.32 


•C. 

103.2 
104.0 
104.  5 
105.5 
106.5 


Good;  a  trifle  tough . . 
Excellent;  rather  firm 

Excellent;  mellow 

Fair;  a  trifle  gummy . 
Thick  sirup 


Taste. 


Excellent;  tart. 
Excellent. 
Excellent;  mild. 

Do. 
Sweet. 


1  Analysis  of  juice:  Brix,  7.0;  pectin  number,  5$;  acidity  (as  H2SO4),  0.99  per  cent. 

2  Reference  to  ''consistency''  and  "taste"  columns  of  a  jelly  series  shows  that  the  ratio  of  sugar  to  U3e 
depends  upon  the  quality  of  the  jelly  desired. 

The  following  conclusions  are  evident  from  Tables  9  and  10:  IS 
(1)  The  maximum  sugar  ratio  for  the  common  guava  is  If,  and  for 
the  strawberry  guava,  1J;  (2)  the  quantity  of  jelly  increases  with 
the  increase  in  sugar  ratio,  but  the  increase  is  not  proportional; 
(3)  the  percentage  of  sugar,  as  well  as  the  specific  gravity,  and  the 
boiling  temperature  of  the  jelly,  increase  with  the  increase  in  the 
sugar  ratio;  (4)  the  texture  changes,  with  increasing  sugar  ratio, 
from  tough  to  excellent,  mellow,  gummy,  or  sirupy,  in  the  order 
named;  and  (5)  the  jelly  becomes  gummy  or  sirupy  when  the  pro- 
portion of  added  sugar  in  the  jelly  is  about  68  per  cent  or  more 
(approximately  70  per  cent  total  sugar),  and  it  becomes  tough 
when  the  proportion  of  added  sugar  is  less  than  60  per  cent  (approxi- 
mately 62  per  cent  total  sugar) . 

Maximum  sugar  ratio  of  guava  juices. — Table  11  gives  in  condensed 
form  the  maximum  sugar  ratio  of  a  number  of  guava  juices  as 
determined  by  the  foregoing  method. 

Table  11. — Maximum  sugar  ratio  of  guava  juices.® 


Source  o 
fruit. 

Juic( 

No. 

of 

juice. 

Source  of 
fruit. 

Juice 

No. 

of 
juice. 

1 
I     Brix     :  Acidity 

reading.  a**^ 

Maxi- 
Pectin    mum  : 

Brix  U^y 

Maxi- 
Pectin  mum 

No.      sugar 
ratio. 

reading. 

H:S04). 

No.      sugar 
ratio. 

Degrees.  Per  cent. 

Degrees. 

Per  cent. 

1 

Manoa. 

2.0           1.32 

31  '          li 

8  :  Manoa . . . 

8.7 

1.32 

9            H 

2 

...do.... 

5.  5          1. 05 

H         if 

•9  i  Kailua... 

4.7 

.42 

5£              1 
3            }| 

3 

...do.... 

6.0          1.13 

6               If 

10 

...do 

6.7 

.72 

4 

...do.... 

7. 1           1.  51 

7               2 

11 

...do 

0.  O 

.81 

H 

5 

...do.... 

7.2           1.03 

|       l\ 

12 

...do 

6.5 

.83 

n    i 

6 

...do.... 

S.  5           1. 39 

13 

...do 

.        9.4 

.82 

7 

...do.... 

S.l           1.66 

%            2} 

I 

a  The  term  "maximum  sugar  ratio"  is  used  to  denote  the  maximum  number  of  cupfuls  of  sugar  which 
can  be  added  to  one  cupful  of  juice  to  produce  a  jelly  of  good  consistency. 

a  It  is  not  claimed  that  the  figures  given  in  a  jelly  series  should  be  considered  in  the  light  of  accurate 
quantitative  results.  The  personal  factor  undoubtedly  enters  to  a  considerable  extent.  However,  a  nas 
always  been  found  possible  to  duplicate  a  series  closely  enough  to  draw  substantially  the  same  conclusions. 
The  advantage  of  this  method  is  that  it  affords  a  means  of  systematically  studying  the  effect  of  variation 
in  the  sugar  ratio. 


JELLY   MAKING   WITH   HAWAIIAN   FRUITS. 


11 


From  Table  11  it  is  apparent  that  there  is  a  close  relationship 
between  the  Brix  reading  of  the  Manoa  juice,  the  pectin  number, 
and  the  maximum  sugar  ratio.  The  sugar  ratio  is  lower  for  the 
Kailua  juices  than  it  is  for  the  Manoa  juices  due  to  the  low  acidity 
of  the  former. 

G-uava  pectin  table. — Table  12  has  been  constructed  to  give  the 
maximum  sugar  ratio  of  a  guava  juice  when  either  the  Brix  reading 
or  the  pectin  number  is  known. 

Table  12. — Guava  pectin  table.'- 


Brix 
reading. 

Pectin 
No. 

Maxi- 
mum 
sugar 
ratio. 

Brix 
reading. 

Pectin 
Xo. 

Maxi- 
mum 
sugar 
ratio. 

Brix 
reading. 

Pectin 
No. 

Maxi- 
mum 
sugar 
ratio. 

3.  5 
3.  5-5.  5 

31  |i 

11 

5.  5-6.  5 
6. 5-7.  5 

? 

7.5-8.5 
S.  5-9.  5 

7i-8i 
3J-9 

21 

2* 

1  The  above  table  is  based  upon  the  data  given  in  Table  11  on  Manoa  guavas.  The  use  of  the  Brix  read- 
ing in  this  connection  is  not  recommended  because  the  relationship  between  the  Brix  and  the  pectin  number 
is  not  a  constant  one.  It  is  not  to  be  inferred  that  the  maximum  sugar  ratio  is  recommended  as  the  best 
ratio.    It  merely  indicates  the  maximum  amount  of  sugar  which  will  produce  a  jelly. 

The  juice  should  have  an  acidity  of  1  per  cent  or  more  when  the 
guava  pectin  table  is  used.  If  the  acidity  is  less  than  1  per  cent,  the 
maximum  sugar  ratio  will  be  less.  The  texture  of  the  jelly  will  be 
improved,  however,  if  the  acidity  is  increased  rather  than  the  sugar 
decreased. 

Inversion  of  sugar. — In  jelly  making  inversion  of  sugar  is  considered 
necessary  to  prevent  crystallization  of  the  sucrose.  The  amount  of 
inversion  required,  however,  has  not  been  determined.  Goldthwaite18 
failed  to  note  any  crystallization  in  jellies  containing  as  low  as  1.76 
per  cent  or  as  high  as  47.46  per  cent  of  the  added  sugar  inverted. 

To  discover  the  relationship  between  the  sugar  ratio  and  the 
percentage  of  inversion,  the  invert  sugar  was  determined  in  each  of 
several  samples  of  jelly,  the  juice  of  which  had  the  composition 
shown  in  Table  13. 

Table  13. — Composition  of  juices  studied  to  determine  the  relationship  between  the  sugar 
ratio  and  the  percentage  of  inversion. 


Constituent. 


Pro- 
portion. 


Constituent. 


Sucrose 

Reducing  sugar . 


Per  cent. 

0. 71      Pectin  (alcohol  precipitate ) 
3. 01      Acidity  (as  H?S04) 


16  Jour.  Indus,  and  Engin.  Chem. 
43822—23 3 


(1910)  No.  11,  p.  459. 


Pro- 
portion. 


Per  cent. 
1.06 

1.54 


12  BULLETIN   47,   HAWAII   EXPERIMENT   STATION. 

Table  14  shows  the  relation  of  sugar  ratio  to  inversion  of  sugar.17 

Table  14. — Relation  of  sugar  ratio  to  inversion  of  sugar. 


Length 

Total 

sugar 

in 

jelly. i 

Total 

Invert 
sugar 

in 
jelly  .s 

Acid 

Specific 

Final 

Sugar 
ratio. 

of  time 
required 

Weight 
of 

sucrose 
added 

Sucrose 
in 

Sucrose 
in- 

in 
jelly 

gravity 
of 

boiling 
tem- 

for 

jelly. 

to 

jelly.< 

verted.5 

as 

jelly 

pera- 

cooking. 

jelly  .2 

(H2S04)." 

80°  C. 

ture. 

Minutes. 

Grams. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

c  C. 

i 

» 

8* 

177 
261 

61.64 
60.96 

57.48 
58.13 

29.16 
28.04 

33.74 
34.19 

41.32 
41.18 

2.13 
1.44 

102. « 

§ 

1.26 

103.5 

] 

6^ 

335 

62.42 

60.21 

26.68 

36.96 

38.61 

1.13 

1.28 

104.0 

H 

6 

397 

65.26 

63.41 

24.42 

41.98 

33.79 

.95 

1.29 

104.0 

li 

5* 

467 

66.19 

64.61 

21.74 

45.46 

29.64 

.81 

1.29 

104.5 

i! 

6 

536 

66.99 

65.62 

23.16 

44.93 

31.53 

.70 

1.30 

104.5 

2 

5 

584 

70.05 

68.79 

22.42 

48.69 

29.22 

.65 

1.31 

105.5 

:  Added  sugar  plus  total  sugars  of  juice  divided  by  weight  of  jelly. 

2  Added  sugar  plus  sucrose  of  juice  divided  by  weight  of  jelly. 

3  Invert  sugar  (Munson- Walker  method)  divided  by  weight  of  jelly. 

*  (Percentage  of  invert  sugar  in  jelly  minus  reducing  sugars  of  juice)  X0.95  subtracted  from  percentage 
of  total  sucrose  added  to  jelly . 

6  (Percentage  of  invert  sugar  in  jelly  minus  reducing  sugars  of  juice)  X0.95  divided  by  percentage  of  total 
sucrose  added  to  jelly. 

6  (Percentage  of  acid  in  juice  X  245)  divided  by  weight  of  jelly. 

From  Table  14  it  is  evident  that  inversion  takes  place  rather 
rapidly,  only  eight  and  one-half  minutes  being  required  to  invert 
41.30  per  cent  of  the  sucrose  and  five  minutes  to  invert  29.22  per  cent. 
The  total  percentage  of  invert  sugar  in  the  jelly  resulting  from  a 
sugar  ratio  of  one-half  is  only  6.74  per  cent  greater  than  that  from  a 
sugar  ratio  of  2.  It  seems  probable,  therefore,  that  there  is  suffi- 
cient inversion  in  the  highest  sugar  ratios  to  prevent  crystallization. 

VARIATION  IN  ACIDITY. 

To  determine  the  effect  upon  guava  jelly  of  varying  the  acidity  of 
the  juice,  different  quantities  of  citric  acid  were  added  to  four  portions 
of  the  same  juice  in  which  the  pectin  content  remained  constant. 
Table  15  shows  the  variations  in  the  jellies  which  were  obtained  from 
each  portion. 

Table  15. —  Variation  in  acidity  of  juice  with  a  constant  pectin  content.^ 

ACIDITY   OF  JUICE,  0.72  PER  CENT. 


Sugar 
ratio. 

Weight 
of  jelly. 

Propor- 
tion of 
sugar 
to  jelly. 

Acidity 
of  jelly 

(as 
H2S04)> 

Consistency. 

Taste. 

3 
I4 

u 
n 

Grams. 
237 
305 
364 
375 

Per  cent. 
63.3 
65.6 
68.7 
80.0 

Per  cent. 

0.74 

.57 

.48 
.46 

Firm;  mellow 

do 

do 

Poor;  gummy 

Good. 
Too  sweet. 
Rather  sweet. 
Do. 

ACIDITY   OF  JUICE,   1.17  PER  CENT. 


1\ 
li 
if 

396 
458 
514 
541 

63.1 
65.5 
68.0 
73.9 

0.72 
.62 
.55 
.53 

Excellent 

do 

Excellent;  a  trifle  mellow 

Too  tart. 
Excellent. 
Do. 

2 

Pnnr;  gummy 

Too  sweet. 

a  Analysis  of  juice:  Brix,  6.7;  pectin  No.  6f:  acidity  (as  H2SO4),  0.72  per  cent. 
i>  (Percentage  of  acid  in  juiceX245)  di Aided  by  weight  of  jelly. 

17  No  crystallization  observed  in  any  of  the  jellies  after  6  months'  standing. 


JELLY   MAKING  WITH    HAWAIIAN   FRVITS.  13 

Table  15. —  Variation  in  acidity  of  juice  with  a  constant  pectin  content — Continued. 

ACIDITY   OF  JUICE,  1.4   PER,  CENT. 


Propor- 

Acidity 

Sugar 

Weight 

tion  of 

of  jelly 

ratio. 

ol  jelly. 

sugar 
to  jelly. 

(as 

H,S04). 

Grams. 

Per  cent. 

Per  cent. 

if 

518 

67.5 

0.66 

2                595 

67.2 

.57 

2\  1            652 

69.0 

.52 

2* 

688 

72.6 

.50 

Consistency. 


Taste. 


Excellent 

Good;  a  trifle  mellow 

Fair:  mellow;  a  trifle  gummy . 
Very  mellow;  sirupy 


Excellent. 
Do. 

A  trifle  sweet . 
Rather  sweet. 


ACIDITY   OF   JUICE.   1.62   PER   CENT. 


705  I  70. 


0. 56     Poor;  rather  mellow Rather  sweet 


From  Table  15  it  is  concluded  that  the  maximum  sugar  ratio 
increases  with  the  acidity.  A  guava  juice  having  a  pectin  number 
of  6f,  which  is  a  medium  juice,  requires  an  acidity  of  at  least  1.4 
per  cent  for  the  highest  sugar  ratio.  When  the  acidity  is  less  than  1.4 
per  cent,  the  pectin  can  not  swell  to  its  maximum  capacity. 

To  produce  a  jelly  of  about  the  proper  tartness,  a  juice  of  0.71 
per  cent  acidity  requires  a  sugar  ratio  of  about  three-fourths:  a  juice 
of  1.17  per  cent  acidity  requires  about  1J;  and  1.4  per  cent  acidity, 
a  sugar  ratio  of  about  2. 

Poor  consistency  results  when  the  proportion  of  acidity  in  the 
jelly  is  approximately  0.5  per  cent  or  less.  Although  the  acidity 
can  be  much  higher  than  0.5  per  cent  without  exerting  a  harmful 
effect  on  the  consistency  of  the  jelly,  the  taste  becomes  tart  when  the 
proportion  of  acid  in  the  jelly  is  about  0.75  per  cent  or  over.  It 
seems,  therefore,  that  the  optimum  acidity  in  guava  jelly  is  between 
0.6  and  0.75  per  cent!  of  the  jelly. 

VARIATION  IN  PECTIN. 

The  effect  of  varying  the  pectin  content  of  guava  juice  with  a 
constant  proportion  of  acidity  was  studied  by  diluting  portions  of 
a  guava  juice  with  different  quantities  of  water  and  bringing  them 
to   a  uniform  acidity  with  citric  acid. 

Table  16  shows  the  composition  of  the  juices  in  which  the  propor- 
tion of  acidity  remained  constant. 

Table  16. — Composition  of  guava  juices  in  which  the  pectin  content  was  varied  and  the 
acid  content  remained  constant. 


Juice. 

Brix 
reading. 

Pectin    f  Acidity 
-No-       i  H2SO<). 

A 

Digrus. 
2.6 
5.1 
7.9 

Per  ee/it. 
3i  1            1.40 

B 

5|  I            1.40 
7£               1.40 

C 

14 


BULLETIN  47,   HAWAII  EXPERIMENT  STATION. 


Table  17  shows  the  effect  upon  the  jellies  obtained  from  juices 
having  a  constant  acidity  but  varying  pectin  contents. 


Table  17. 


-Effect,  upon  the  jellies  obtained  from  juices  having  a  constant  acidity  but 
varying  pectin  contents.' 


JUICE    A. 


Sugar 
ratio. 

Weight 
of  jelly. 

Propor- 
tion of 
sugar 

to  jelly. 

Propor- 
tion of 
pectin 

in  jelly.1 

Consistency 

Taste 

| 

Grams. 
221 
294 
346 
400 

Per  cent. 
67.8 
68.0 
72.3 
75.0 

Per  cent. 

0.58 

.44 

.37 

.32 

Excellent;  tender 

1* 

Very  tender 

Do. 

do 

Sirupy 

Tart;  mild. 
Good. 

JUICE    3. 

if 

401 
447 
519 
.569 
615 

62.3 
67.1 
-37.4 
70.3 

0.-53 
.48 
.41 
.37 
.35 

Excellent;  tender 

do 

Verv  tender 

Tart. 
Excellent. 
Excellent;  mild. 

2 

2i 

do 

Sirupy 

Excellent;  too  sweet. 
Too  sweet. 

JUICE   C. 

I' 

471 
538 
576 
637 

63.7 
65.1 
69.4 
70.6 

0.59 
.52 

.48 
.44 

Excellent,  firm 

do 

....do 

Excellent 
Do. 

% 

Good:  too  tender 

1  (Pectin  number  of  juiceX0.15lx245)  divided  by  (weight  of  jellyxlOO). 

From  Table  17  it  is  concluded  that  (1)  the  maximum  sugar  ratio 
increases  with  the  pectin  content;  (2)  a  medium  guava  juice,  which 
contains  a  pectin  content  of  about  7-J  is  capable  of  forming  a  jelly 
having  a  sugar  ratio  of  2,  provided  sufficient  acid  is  present;  and  (3) 
the  consistency  becomes  too  tender  for  a  good  jelly  when  the  propor- 
tion of  pectin  in  the  jelly  falls  below  about  0.48  per  cent,  and  it 
becomes  tough  when  the  proportion  of  pectin  is  about  0.7  per  cent 
or  over. 

OTHER  HAWAIIAN  FRUITS  FOR  JELLY  MAKING. 

Although  there  are  many  fruits  in  Hawaii  that  give  palatable 
jellies ,  the  actual  number  which  can  be  used  for  jelly  making  is 
rather  limited.  Fruits  that  are  commonly  grown,  such  as  the  papaya, 
the  avocado,  and  the  mango,  are  not  adapted  to  jelly  making. 
" Papaya  jelly"  is  occasionally  made  by  adding  pectin  and  citric 
acid  to  the  papaya  fruit.  The  mango  contains  sufficient  pectin  and 
acid  for  jelly  making,  but  its  yield  is  rather  small  to  be  of  commer- 
cial use  for  jelly  making,  when  the  cost  of  the  fruit  and  the  time 
required  to  prepare  the  juice  are  considered. 

Next  in  importance  to  the  guava  is  the  poha  (Physalis  peruviana) . 
the  jelly  of  which  is  much  in  demand.  Commercial  jelly  companies 
in  Hawaii  are  often  unable  to  fill  their  orders  for  poha  jelly,  owing 
to  the  small  quantity  of  poha  fruit  grown.  The  roselle  (Hibiscus 
sdbdariffa)  ranks  third  in  commercial  importance.  This  fruit  can 
generally  be  purchased  on  the  markets  during  the  fruiting  season, 
but  owing  to  its  lack  of  popularity  it  is  sold  in  small  quantities. 


JELLY   MAKING   WITH   HAWAIIAN   FRUITS. 


15 


Jelly  from  the  Isabella  grape  (Vitis  labrusca)  is  commonly  made  in 
the  home.  This  grape  can  be  purchased  on  the  markets  nearly  the 
year  round.     The  poha,  roselle,  and  Isabella  grape,  together  with  the 

fuava,  are  the  only  fruits  which  are  grown  in  sufficient  quantities  to 
e  of  any  importance  for  jelly  making  at  present. 
The  methods  worked  out  for  the  guava  were  used  in  making  jelly 
from  the  grape,  the  roselle,  and  the  poha. 

ISABELLA  GRAPE  (Vitis  labrusca).  * 

A  representative  juice  (juice  B,  Table  18)  showed  the  following 
analysis : 

Table  18. — Composition  of  Isabella  grape  juice. 


Constituent.                           ^tfim*' 

Constituent.                             i*g£f- 

Sucrose 

Per  cent. 

!  Per  cent. 
Pectin  (alcohol  precipitate) 0. 92 

Reducing  sugars 

10.18 

Acidity  (as  H2S04) 1.21 

Proportion  of  water  to  fruit  for  grape  jelly. — To  determine  the  best 
proportion  of  water  to  fruit,  three  10-pound  lots  of  grapes  were 
cooked  with  varying  proportions  of  water.  Gentle  boiling  was  main- 
tained for  only  20  minutes,  during  which  time  complete  disintegra- 
tion of  the  fruit  had  taken  place.  Each  lot  was  then  strained  through 
cheesecloth,  after  which  the  pulp  was  squeezed  to  remove  any 
remaining  portions  of  the  juice. 

Table  19  shows  the  composition  of  grape  juice  made  with  different 
proportions  of  water  and  fruit. 

Table  19. — Composition  of  grape  juices  resulting  from  varying  proportions  of  water 

and  fruit. 


'  Pounds 

1  of  water 

Juice.                   to  10 

pounds 

grapes. 

Total 
juice. 

Brix 
reading. 

Total 
sugars. 

Pectin 

No. 

Acidity 

(as 
H2S04). 

Total  » 

pectin 

extracted. 

Total 
acid  ex- 
tracted 

(as 
H2S04). 

A.. 

Pounds. 
0.5 

Cubic  cen- 
timeters. 
3,140 
4,055 
5,3-50 

Decrees. 

'  15.  2 

12.6 

10.1 

Per  cent. 

11.91 

10.18 

8.07 

5i 

Per  cent. 

1.37 

1.21 

95 

Grams. 
36.6 
3S.2 
38  6 

Grams. 
43.00 

B 

3.0 

49.07 

c 

fi  =1 

50  31 

1  Pectin  number  X0.222Xcubic  centirnerers  juice  divided  by  10). 

A  study  of  Table  19  shows  that  there  is  nothing  to  be  gained  in 
adding  more  than  3  pounds  of  water  to  10  pounds  of  grapes,  because 
a  greater  amount  does  not  result  in  appreciably  greater  extraction. 

13  The  Isabella  variety  has  shown  remarkable  adaptability  to  the  climatic  and  soil  conditions  >f  Hawaii 
and  far  surpasses  all  other  varieties  in  acreage.    It  is  usually  spoken  of  as  the  Hawaiian  grape. 


16 


BULLETIN    47,    HAWAII   EXPERIMENT   STATION 


Sugar  ratio  for  grape  jelly. — Table  20  shows  the  results  of  running 
a  jelly  series  on  each  of  the  juices  given  in  Table  19. 

Table  20. — Results  of  varying  proportions  of  sugar,  pectin,  awl  acid  in  grape  jelly.1 

JUICE  A. 


Sugar 
ratio 


Length 

of 

time 

re- 
quired 

for 

Weight 

of 
jelly. 

cook- 

ing. 

Mia. 

Gms. 

3 

342 

2* 

378 

H 

432 

5 

481 

6 

536 

7 

608 

Pro- 

por-  Total 

tion  sugar 

of  in 

sugar  jelly, 
added. 


Spe-  Boil- 

cific  ing 

grav-  tem- 

ity  pera- 

"°C.  tures. 


Pec- 
tin 
in 
jelly.* 


Acid 

in 
jelly. s 


Consistency. 


Taste. 


P.ct. 
43.8 
52.9 
57 

62.4 
65.3 

65.  S 


7.9 


P.ct. 
52.4 
60.6 
64.6 
68.4 
70.7 
70.6 


1.21 
1.25 
1.27 
1.27 
1.29 
1.28 


°C. 

102.0 
103.0 
103.5 
104.0 
105.5 
105.5 


P.ct. 
0.83 
.76 
.66 
.60 
.53 


P.  ct. 
0.98 
.89 
.78 
.70 
.63 
.55 


Finn;  tender Too  tart. 

do ,  Tart. 

do Excellent. 

do Do. 


Mellow;  lacks  body 
do 


Rather  sweet. 

Sweet. 


.TCTCE  B. 

3 
l4 

n 

5 
4 

4 
5 

366 
421 
445 

52.7 
54.6 
59.4 
07.4 

61.4  1 

61.5  1 
65.3  ] 
73.0 

1.25 
1.25 
1.27 
1.29 

103. 0 
103.  5 
104.0 
105.0 

0.82 
.63 
.55 
.52 

1.04 
.81 
.70 
.67 

Firm;  tender 

do 

do 

Mellow;  lacks  body. 

Tart. 
Excellent. 

Do. 
Rather  sweet. 

JUICE  C. 

4 

3 

222 

45.0 

53.9 

1.22 

103.  5 

O.SO 

1.05 

i 

6i 

266 

58.4 

63.8 

1.26 

104.5 

.66 

.88 

1 

5* 

327 

61.2 

67.2 

1.27 

104.5 

.54 

.71 

li 

6 

375 

66.7 

71.9 

1.29 

105.  0 

.47 

.62 

Firm:  tender. 

....do 

....do 


.  62     Mellow:  lacks  body . 


Too  tart. 
Excellent. 

Do. 
Rather  sweet. 


1  These  jellies  were  left  exposed  to  the  air.  All  jellies  having  a  sugar  ratio  of  less  than  1  developed  mold. 
Those  having  a  sugar  ratio  of  1  or  more  did  not  develop  mold  in  3  weeks'  standing.  No  crystallization 
occurred  in  anv  of  the  lots. 

8  (Pectin  number  of  juice  X0.222X245)  divided  by  (weight  of  jellyxlOO). 

3  (Per  cent  acid  in  juice  X245)  divided  by  weight  of  jelly. 


From  Table  20  it  is  evident  that  (1)  the  maximum  sugar  ratios  of 
juices  A,  B,  and  C  are  1£,  li,  and  1,  respectively:  (2)  the  minimum 
proportion  of  pectin  necessary  to  produce  a  jelly  with  sufficient  body 
is  about  0.56  per  cent  of  the  jelly;  (3)  the  acidity  of  grape  juice  is 
probably  never  the  limiting  factor  in  jelly  making,  since  the  best 
flavors  were  produced  with  acidities  of  from  0.7  to  0.85  per  cent  of 
the  jelly;  (4)  the  jelly  either  lacks  body  or  is  of  a  mealy,  granular 
texture  whenever  the  total  sugar  in  grape  juice  is  about  67.0  per  cent 
or  over,  and  mold  is  likely  to  develop  when  the  total  sugar  is  less 
than  about  60  per  cent;  and  (5)  the  maximum  sugar  ratios  of  the 
grape  juices,  as  determined  by  the  above  table,  are  about  one-fourth 
lower  than  is  given  in  the  guava  pectin  table  for  the  same  pectin 
numbers. 

NOTES    ON    JELLY    MAKING    FROM    THE   ISABELLA    GRAPE. 

Grape  jelly  is  characterized  by  its  very  tender  texture.  Over- 
cooking guava  jelly  results  in  a  tough,  hard  consistency,  but  over- 
cooking grape  jelly  causes  an  apparent  breaking  down  of  the  pectin, 
which  becomes  a  soft,  granular  mass.  Grape  jelly  should  not,  there- 
fore, be  overcooked. 


JELLY   MAKING  WITH   HAWAIIAN   FRUITS. 


17 


Too  high  a  sugar  ratio  shows  itself  in  lack  of  body,  the  felly 
literally  "melting  in  ones  mouth."  Undisturbed  in  the  glass,  this 
jelly  may  have  the  excellent  sharp  cleavage  of  a  perfect  jelly,  but 
turned  from  its  mold,  it  falls  apart:  or  in  other  words,  it  has  failed 
to  jell. 

Grape  jelly  should  be  made  in  small  batches  in  a  relatively  large 
container  so  that  evaporation  will  be  rapid.  Mealy  or  granular 
texture  was  found  to  result  when  the  jelly  was  allowed  to  boil  over 
10  minutes. 

All  the  grape  jellies  showed  considerable  tendency  to  "weep" 
regardless  of  the  sugar  ratio.  "Weeping"  is  doubtless  due  to  the 
weak  nature  of  the  colloidal  membrane  of  the  grape  pectin.  This  is 
substantiated  bv  the  fact  that  adding  a  small  amount  of  apple  pectin 
to  grape  jelly  will  not  only  stop  "weeping  "  but  also  greatly  strengthen 
the  texture  of  the  jelly. 

ROSELLE   (Hibiscus  sabdariffa). 

Analysis  of  rosette  juice. — Analysis  of  representative  roselle  juice 
(juice  D,  Table  21)  gave  the  following  results: 

Table  21. — Composition  of  rosdle  juice. 


Constituent. 

Prop  or-  i 
tion.     | 

Constituent. 

Propor- 
tion. 

Per  cent. 

Per  cent. 
0.95 

Reducing  sugars 

0. 21 

Acidity  (as  H-SOO 

.91 

Proportion  of  water  to  fruit  for  roselle  jelly. — Varying  amounts  of 
water  were  added  to  live  3-pound  lots  of  roselle  to  determine  the  best 
ratio  of  water  to  fruit  from  which  the  seed  pods  were  not  removed. 
Gentle  boiling  was  maintained  for  20  minutes,  when  it  was  found 
that  the  calyxes  had  completely  disintegrated.  Each  lot  was  then 
strained  through  cheesecloth  and  squeezed  as  dry  as  possible. 

Table  22  gives  the  composition  of  roselle  juices  made  from  varying 
proportions  of  water  and  fruit. 

Table  22. — Composition  of  roselle  juices  resulting  from  varying  proportions  of  water 

and  fruit. 


Pounds 
of  water 

to  3 
pounds 

roselle . 

Total 
juice. 

Erix 
reading. 

Pectin 

N  v 

Acidity    Total  pec- 

(as          tin  ex- 
H2S04).    tracted.1 

Total 
acid  ex- 
tract ed(  as 

.V- 

Pounds. 
3 

4.5 
6 

7.5 
9 

Cubic 
centimeters 

Degrees. 

Per  cent,     (farms. 

Grams. 

R 

1 .  660 
2.120 

2,980 
3,730 

5.2 

4.3 
3.S 
3.1 

61 

6 
5 

45 

1.17             19.3 
.  98             23.  7 
.  55             27. 7 
.74             29.5 

19.  4° 

C 

20.78 

D 

25.33 

E . . .  . 

27.60 

1  Pectin  number  X0.18*ixcubic  centimeter  of  juice  divided  by  100. 

1  The  juice  formed  a  semijelly  and  would  not  pass  through  the  cheesecloth  bag. 


18 


BULLETIN   47,   HAWAII  EXPERIMENT  STATION. 


Table  22  shows  that  with  increasing  proportions  of  water,  both 
extraction  of  pectin  and  acidity  increased:  and  that  with  dilution 
greater  than  that  of  juice  D  the  pectin  and  acid  content  are  so  low 
that  the  juice  can  be  sufficiently  concentrated  for  jelly  making  only 
by  prolonged  boiling. 

Composition  of  different  parts  of  the  roselle  plant. — Wester  19  states 
that  the  leaves  and  stalks  of  the  roselle  can  be  used  for  jelly  making 
and  recommends  the  removal  of  the  seed  pods  from  the  calyxes 
before  cooking. 

To  learn  whether  these  statements  are  applicable  to  the  roselle  in 
Hawaii,  it  was  decided  to  experiment  by  separating  a  single  whole 
roselle  plant  into  three  portions;  (1)  the  mature  fruit;  (2)  the  imma- 
ture fruit,  blossoms,  leaves,  and  tender  ends  of  the  stem;  and  (3) 
the  remaining  woody  stalks.  The  mature  fruits  were  then  separated 
into  calyxes  and  seed  pods. 

The  juices,  the  composition  of  which  is  given  in  Table  22,  were 
prepared  as  follows : 

A.  Calyxes  weighing  1.91  pounds  were  separated  from  3  pounds  of 
mature  fruit  and  boiled  with  4.5  pounds  of  water  for  20  minutes. 
The  mass  was  then  drained  through  a  cheesecloth  bag  and  squeezed 
as  dry  as  possible. 

B.  Seed  pods  weighing  1.09  pounds  were  extracted  from  3  pounds 
of  mature  fruit  and  boiled  with  4.5  pounds  of  water  for  20  minutes. 
The  juice  was  then  completely  drained  and  boiled  down. 

C.  Three  pounds  of  mature  fruit  from  which  the  seed  pods  were 
not  removed  were  treated  like  that  of  series  A. 

D.  The  immature  blossoms,  leaves,  etc.,  of  a  single  roselle  plant, 
weighing  0.93  pound,  were  chopped  fine,  boiled  with  2  pounds  of 
water  for  30  minutes,  and  the  juice  was  completely  drained  off. 

E.  The  stalks,  immature  blossoms,  leaves,  etc.,  of  a  single  roselle 
plant,  weighing  0.98  pound,  was  cut  into  short  lengths  and  boiled 
with  2  pounds  of  water  for  30  minutes,  after  which  the  juice  was 
completely  drained  off. 

Table  23  gives  the  results  of  analysis  of  the  roselle  plant. 

Table  23. — Composition  of  the  roselle  plant. 


Part?  of  individual  pl2r.1t. 

Total 
juice. 

Brix 
reading. 

Pectin      Acidity 
No.             (as 

H2S04). 

Total 
Total  pec-   acid  ex- 
tin  ex-    tracted(as 
tracted.i    H2SO4). 

A.  Calyxes 

Cubic     j 
centimeters  Degrees. 
1,700  j           2.7 
315              3. 4 

Per  cent.     Grams.       Grams. 
4J             0.78             13.4             13.26 

B,  Seed  pod 

2"  1            .34  1            1.2 

1.07 

C,  Whole  fruit 

1,680 
660 
610 

3.4 
3.2 
1.3 

3 

(3) 

.84 
.64 
.10 

14.9 
3.1 

14.11 

I>,  Leaves,  stems,  etc.2 

4.22 

.61 

'  Pectin  number  X0.186xcubic  centimeter  of  juice  divided  by  100. 
2  Immature  blossoms,  leaves,  etc.  of  a  single  plant. 
1  Trace. 


From  Table  23  it  is  apparent  that  the  calyx  of  the  roselle,  as 
grown  in  Hawaii,  is  the  only  part  of  the  plant  containing  sufficient 
pectin  and  acid  to  make  it  of  value  for  jelly  making.  The  leaves, 
tender  shoots,  and  immature  calyxes  do  not  contain  sufficient  pectin 


«  Prog.  Agr.,  5  (1&21),  No.  7,  p.  18. 


JELLY    MAKING   WITH    HAWAIIAN    FRUITS. 


19 


to  make  them  practicable  for  use  in  jelly  making,  and  the  flavor  of 
the  jelly  made  from  them  was  not  appetizing,  although  it  had  an 
excellent  consistency. 

Jellies  made  from  the  calyxes  and  from  the  whole  fruit  were  com- 
pared for  taste  and  consistency.  It  was  impossible  to  detect  any 
difference,  and  since  the  separation  of  calyxes  and  seed  pods  is  a 
rather  tedious  process,  the  operation  seems  a  needless  expenditure 
of  time. 

Sugar  ratio  for  roselle  jelly. — Table  24  gives  the  results  obtained 
from  a  jelly  series  made  from  juices  B,  D,  and  E. 

Table  24. — Results  of  varying  proportions  of  sugar,   pectin,  and  acid  in  roselle  jelly. 

JUICE  3  (seed  pods).    • 


Sug-                    Propor- 
ar      Weight     tion  of 
ra-     of  j  mv.    sugar  to 

tio.                      jelly.1 

I 

Propor- 
tion of 
pectin 

in  jelly. 

Acidity 
of  idly 

(as 
H2804). 

Consistency. 

Taste. 

1                1 
Grams.     Percent. 
1               316           63.3 

Percent. 
0.90 
.73 
.62 
.56 
.52 
.48 

Per  ecu?. 
0.91 
.74 
.63 
.57 
.52 
.4S 

Good;  firm:  tender 

1J             391           63.9 
11             460           65.2 
11            505           69.3 
2               552           72. 5 
21-             597           75. 4 

do 

Excellent;  firm:  tender 

do... 

Too  mellow * 

do 

Do. 

Excellent :  strong  flavor. 

Excellent. 

Too  sweet:  mild. 

Too  sweet. 

JUICE  D  (leaves,  stems,  etc. 


1 

68 

73.5 

1 

157 

63.7 

.1 

231 

65.0 

1 

301 

66.4 

H 

365 

68.5 

IV 

410 

73.2 

If 

449 

77.9 

2 

520 

77.0 

.62 


3.06 

1.33 

.90 


.51 
.46 
.40 


Thick  sirup 

Fair;  rather  sirupy 

Good;  firm:  tender 

Excellent;  firm;  tender.. 

Excellent 

Slightly  lacking  in  body. 

Lacking  in  body 

Sirupy 


Too  tart:  strong  flavor. 

Do. 
Tart. 
Excellent;  mild. 

Do. 

Do. 
Too  sweet. 

Do. 


JUICE  E  (large  stalks). 


1 

218 

68.8 

.89 

.S3 

1 

287 

69.7 

.67 

.63 

U 

334 

74.  8 

.58 

.54 

11 

381 

7^.7 

.51 

.48 

Firm;  tender Excellent;  tart;  mild. 

....do I         Do. 

Too  mellow Excellent:  mild. 

Sirupy j  Do. 


1  The  proportion  of  total  sugars  in  the  jell}*  was  not  determined,  since  the  fruit  sugars  in  roselle  juice  are 
negligible. 


From  Table  24  it  is  concluded  that  (1)  the  maximum  sugar  ratio 
of  juices  B,  D,  and  E  is  If,  1^,  and  1,  respectively:  (2)  roselle  jelly 
containing  about  72  per  cent  of  sugar,  or  over,  lacks  body,  or  is  sirupy 
and  that  containing  less  than  about  63  per  cent  is  of  very  poor 
consistency:  (3)  the  minimum  pectin  content  necessary  to  give 
sufficient  body  to  roselle  jelly  is  about  0.63  per  cent  of  the  jelly: 
(4)  the  best  flavors  are  produced  from  juices  having  from  0.5  to  0.7 
per  cent  of  the  jelly:  and  (4)  the  maximum  sugar  ratios,  as  deter- 
mined by  Table  24,  are  about  one-fourth  lower  than  is  given  in 
the  guava  pectin  table  for  the  same  pectin  number. 


20 


BULLETIN  47,   HAW  AH  EXPERIMENT  STATION. 


NOTES   ON   JELLY   MAKING   FROM   ROSELLE. 

Roselle  jelly  is  comparatively  easy  to  make.  In  order  that  it 
may  have  sufficient  body,  the  mass  should  be  boiled  for  some  time 
after  the  first  jelly  test  is  made.  A  precipitate  producing  a  very 
stiff  guava  jelly  will  produce  a  roselle  jelly  of  proper  consistency. 

Roselle  jelly  somewhat  resembles  grape  jelly  in  its  tender  con- 
sistency. However,  it  does  not  "weep"  to  the  extent  that  the  latter 
does. 

The  flavor  of  the  roselle  is  very  strong.  Jellies  that  are  made  from 
too  concentrated  a  juice,  or  which  contain  too  small  an  amount  of 
su^ar,  have  a  very  strong  flavor  and  a  deep  red  color.  This  is  prob- 
ably the  chief  cause  of  the  lack  of  popularity  of  the  roselle  jelly. 
If  a  medium  juice — that  is;  one  containing  about  2.5  pounds  of  water 
to  1  pound  of  fruit — and  the  maximum  sugar  ratio  are  used,  the 
resulting  jelly  will  be  milder  flavored  and  lighter  colored. 

POHA  (Physalis  peruviana). 

Analysis  of  poha  juice. — Juice  of  the  poha  had  the  following  com- 
position : 

Table  25. — Composition  of  poha  juice. 


Constituent. 

Propor- 
tion. 

Constituent.                          Fl?g*- 
tion. 

S  ucrose 

Per  cent. 
2.72 
10.42 

Per  cent. 

Pectin  (alcohol  precipitate) 0. 43 

Acidity  (as  H2S04) 1           1.25 

Reducing  sugars 

Proportion  of  water  to  fruit  for  poha  jelly. — Varying  amounts  of 
water  were  added  to  10-pound  lots  of  poha  to  determine  the  best 
proportion  of  water  to  fruit.  Gentle  boiling  was  maintained  for 
20  minutes  when  it  was  found  that  complete  disintegration  had 
taken  place.  Each  lot  was  then  strained  through  cheesecloth  and 
squeezed  dry. 

Table  26  shows  the  composition  of  juices  obtained  with  varying 
proportions  of  water  and  fruit. 

Table  26. —  Composition  of  poha  juices  resulting  from  varying  proportions  ofuater  and 

fruit. 


Pounds  of  water  to  10  pounds 
of  ponas. 

Total 
juice. 

Brix 

reading. 

Total 
sugar. 

Pectin 
No. 

Acidity 

(as 
H2SO4). 

Total  1 
pectin 

ex- 
tracted. 

Total 
acid  ex- 
tracted 

as 
(HjSO,). 

A  (none) 

Cubic 
centi- 
meters. 
2,410 

Degrees. 
18.9 

Per  cent. 
15.80 

P 

Per  cent. 
1.65 
1.45 
1.19 

Grams. 
17.6 
18.3 
19.3 

Grams. 
39.77 

B  (1.5) 

3,040  j          15.7           13.12 
3,735 

44.08 

C(4) 

44.45 

1  Pectin  number  X0.172xcubic  centimeter  of  juice  divided  by  106. 


JELLY  MAKING  WITH   HAWAIIAN  FKUITS. 


21 


An  examination  of  Table  26  shows  that  the  best  ratio  of  water 
to  fruit  was  1.5  pounds  of  water  to  10  pounds  of  pohas.  Extrac- 
tion was  then  practically  complete.  With  the  higher  dilutions  the 
pectin  content  was  too  low  for  a  ^ood  jelly  juice. 

Sugar  ratio  for  pofia  jelly. — Table  27  gives  the  results  obtained 
from  a  jelly  series  made  from  juices  A,  B,  and  C  of  Table  26. 

Table  27. — Results  of  varying  proportions  of  sugar,  pectin,  and  acid  in  poha  jelly. 

JUICE  A.i 


Sugar 
ratio. 

Weight 

of 
jelly. 

Propor-     T  t  ,      Propor- 
tion of       x  otai       ticn  of 
sugar     inigw,      pectin 
to  jelly.  ;mleUJ-    in  jelly. 

Propor- 
tion of 
acidity 

(as 
H2S04). 

Consistency. 

Taste. 

1 

li 

1* 

1* 

2 

Gravis. 
338 
394 
455 
510 

541 

Percent. 
59.2 
63.5 
65.9 
68.6 

74.0 

Per  cent. 
70.6 
73.3 
74.4 

76.2 

Sl.l 

Per  cent. 

0.53 

.45 

.39 

.35 

.33 

Percent. 
1.20 
1.03 

.89 
.79 

.75 

Firm;  somewhat  tough Tart;  strong  flavor. 

Firm;  excellent Fair;  strong  flavor. 

do Excellent. 

Firm;  tender Excellent;    rather 

sweet. 
Firm,  but  gummy Rather  sweet . 

JUICE  B.a 


1 

248 

60.5 

73.5 

0.60 

1.43 

1 

323 

61.9 

71.9 

.46 

1.10 

M 

388 

64.4 

72.7  , 

.3S 

.91 

11 

438 

68.5 

75.8 

.34 

.81 

Firm:  somewhat  tough Tart. 

Excellent Excellent. 

do Do. 

Excellent;  tender Do. 


JUICE  C. 


241 

62.2 

73.5 

0.52 

1.21 

310 

64.5 

73.3 

.41 

.94 

372 

67.2 

74.5 

.34 

.78 

435 

69.0 

75.2 

.29 

.67 

470 

74.5 

80.0 

.27 

.62 

Excellent;  tender Tart. 

do Excellent;  mild. 

do Do. 

Firm;  somewhat  gummy...  Fair. 
do Poor. 


1  Dark  colored  and  rather  strong  flavored  series. 
1  Light  colored  and  mild  flavored  series. 

3  Lack  of  juice  prevented  a  higher  sugar  ratio.    However,  the  tender  consistency  of  the  H  sugar  ratio 
indicated  that  a  higher  ratio  would  produce  a  gummy  or  simpy  jelly. 

From  Table  27  it  is  concluded  that  (1)  the  maximum  sugar  ratia 
of  juices  A,  B,  and  C  is  If,  1£,  and  1|,  respectively;  (2)  poha  jelly 
is  much  higher  in  sugar  content  than  is  any  other  jelly  studied; 
(3)  a  jelly  of  excellent  consistency  and  taste  will  result  when  the 
total  sugar  content  is  from  70  to  75  per  cent,  but  the  jelly  will  be 
tough  when  the  sugar  ratio  is  less  than  70  per  cent,  and  gummy  or 
sirupy  when  the  sugar  ratio  is  over  75  per  cent;  (4)  the  minimum 
proportion  of  pectin  required  to  produce  a  good  consistency  is  about 
0.35;  (5)  the  acidity  of  poha  juice  is  probably  never  a  limiting 
factor,  but  the  best  flavors  were  produced  with  acidities  ranging  from 
0.8  to  1.0  per  cent  of  the  jelly;  and  (6)  the  maximum  sugar  ratio 
of  the  poha  juices,  as  determined  by  the  above  table,  are  one-fourth 
to  one-half  higher  than  is  given  in  the  guava  pectin  table  for  the 
same  pectin  numbers. 


22 


BULLETIN  47,   HAWAII  EXPERIMENT  STATION. 


NOTES    OX    JELLY    MAKING    FROM    THE    POHA. 

It  was  found  rather  difficult'  to  produce  a  poha  jelly  having  the 
proper  consistency.  This  is  due  to  the  fact  that  the  resultant 
product  becomes  entirely  too  firm  and  tough  when  the  jelly  is 
allowed  to  cook  until  a  test,  suitable  for  guava  jelly,  is  obtained. 
A  very  soft  jelly  test  must  be  used  to  produce  a  good,  tender  con- 
sistency. 

Owing  to  its  very  high  sugar  content,  poha  jelly  has  a  tendency 
to  crystallize.     If  trie  jelly  is  covered  with  paraffin,  or  hermetically 
capped,  crystallization  can  usually  be  prevented. 

CONSISTENCY  OF  JELLIES  AS  AFFECTED  BY  THE  PHYSICAL  PROPERTIES 

OF  PECTIN. 

A  fruit  jelly  is  essentially  a  colloidal  gel,  throughout  which  sugar 
and  acid  cause  a  uniform  precipitation  of  the  pectin.  The  character 
of  the  resultant  gel  depends  primarily  upon  the  physical  properties 
of  the  pectin.  Extensive  studies  have  been  made  of  the  occurrence, 
extraction,  and  chemical  composition  of  pectins.20  Little  mention, 
however,  has  been  made  of  the  difference  in  their  physical  properties, 
which,  from  the  standpoint  of  jelly  making,  is  of  very  great  importance. 

Observations  on  the  physical  difference  in  the  alcohol  precipitate 
of  the  four  fruit  juiced  (grape,  roselle,  guava,  and  poha)  studied  by 
the  writer  show  that  the  properties  of  jellies  are  closely  related  to 
the  physical  properties  of  their  pectins. 

Table  28  shows  the  relation  existing  between  the  physical  prop- 
erties of  pectins  and  the  resultant  jellies. 

Table  28. — Relation  of  the  physical  properties  of  pectins  to  the  resultant  jellies. 


Fruit. 

Pectin. 

Jelly. 

Grape 

Roselle 

Guava 

Poha 

Very  weak  pectin;  very  short  fibers:  pectin 
mass  easily  broken  apart. 

Weak  pectin;  short  fibers;  pectin  mass  easily 

broken  apart. 
Strong  pectin;  long  fibers;  pectin  mass  spongy 

and  tenacious. 
Very  strong  pectin;  very  long,  dense  fibers: 

pectin  mass  tough  and  stringy. 

Tendency  to  weep;  easily  destroyed  by  over- 
heating; low  sugar  content:  tender-;  lacks 
body. 

Tender;  lacks  body. 

Dense;  plenty  of  body;  tough,  if  overcooked. 

Verv  dense  jelly;  plenty  of  body;  very  tough, 
if 'overcooked;  high  sugar  content. 

Table  28  indicates  that  there  is  a  gradation  of  the  physical  prop- 
erties of  the  pectin  and  jelly  from  grape  through,  to,  and  including 
that  from  poha.  The  pectin  gradually  increases  in  length  of  fibers 
and  tenacity  from  the  gelatinous  grape ,  pectin  to  the  dense,  tough 
poha  pectin.  The  jellies  increase  in  body  and  density  from  the 
tender  grape  jelly  of  low  sugar  content  to  the  tough  poha  jelly  of 
high  sugar  content.  It  seems,  therefore,  that  the  physical  character 
of  the  pectin  is  an  important  factor  in  determining  the  consistency 
of  jelly. 

APPLICATION  OF  THE  GUAVA  PECTIN  TABLE  TO  OTHER  FRUIT  JUICES. 

Reference  of  the  pectin  numbers  of  roselle,  grape,  and  poha  juices 
to  the  guava-pectin  table  shows  that  the  maximum  sugar  ratio  for 
the  roselle  and  grape  juice  is  too  high  by  one-fourth  and  that  the 

20  U.  S.  Dept.  Agr.,  Bur.  Chem.  Bui.  94  (1905),  pp.  67-89. 


.JELLY    MAKING    WITH    HAWAIIAN    FRUITS.  23 

maximum  sugar  ratio  for  poha  juice  is  too  low  by  from  one-fourth 
to  one-half.  These  discrepancies  are  probably  due  to  the  physical 
differences  in  the  pectins  of  the  fruits. 

If  the  physical  differences  are  taken  into  consideration,  the  pectin 
table  for  guavas  can  be  applied  to  most  fruit  juices.  If  the  pectin 
precipitate  forms  a  tender  mass  that  is  easily  broken  apart  when 
the  pectin  number  of  unknown  juice  is  being  determined,  one-fourth 
cupful  of  sugar  should  be  subtracted  from  the  maximum  sugar 
ratio,  as  determined  by  reference  of  the  pectin  number  to  the  guava- 
pectin  table.  If  the  mass  is  very  dense  and  tenacious,  one-fourth 
cupful  should  be  added   to  the  maximum  sugar  ratio. 

SUMMARY. 

Jelly  making  from  tropical  fruits  is  as  yet  an  undeveloped  industry. 

The  writer  conducted  a  series  of  experiments  for  the  purpose  of 
developing  a  systematic  procedure  for  making  jelly  from  any  kind 
of  fruit  containing  sufficient  pectin  and  acid. 

A  method  is  proposed  for  determining  the  '•pectin  number"  which 
can  be  reduced  to  the  approximate  per  cent  of  pectin  by  means  of  a 
common  factor. 

A  table  of  the  maximum  ratio  of  sugar  to  guava  juice  is  given  for  a 
series  of  pectin  numbers.  The  table  may  be  used  for  other  fruit 
juices  provided  the  character  of  the  pectin  is  taken  into  account. 

Experiments  were  made  with  the  guava.  grape,  roselle.  and  poha 
to  determine  their  value  for  jelly  making. 

The  guava  is  especially  well  adapted  for  jelly  making.  It  contains 
a  strong,  fibrous  pectin,  and  usually  has  sufficient  acid.  The  best 
proportion  of  water  to  guava  is  0.75  pound  to  1  pound  of  fruit.  This 
produces  a  juice  of  6  to  7  pectin  number  and  0.8  to  1.14  per  cent 
acidity.     The  maximum  sugar  ratio  for  such  a  juice  is  H  to  If. 

Location,  altitude,  season,  variety,  and  differences  in  the  same 
variety  have  a  very  marked  effect  on  the  acidity  of  guava  juices. 
The  pectin  content  of  all  guava  juice  is  uniformly  high.  It  is  con- 
cluded, therefore,  that  acidity  is  the  only  important  variable  in  guava 
juices  and  that  failure  to  make  jelly  from  the  guava  is  directly  trace- 
able to  lack  of  acidity  in  the  juice. 

The  Isabella  grape  contains  a  very  weak  gelatinous  pectin.  It 
usually  has  sufficient  acid  for  jelly  making.  The  best  proportion  of 
water  to  fruit  is  0.3  pound  to  1  poimd  of  grapes.  This  produces  a 
juice  of  4^  pectin  number  and  1.21  per  cent  acidity.  The  maximum 
sugar  ratio  for  this  juice  is  1J. 

The  roselle  contains  a  rather  weak,  short-fibered  pectin,  but  the 
proportion  of  both  pectin  and  acid  is  sufficient  for  jelly  making. 
The  best  proportion  of  water  to  roselle  is  2.5  pounds  to  1  pound  of 
fruit.  This  produces  a  juice  with  a  pectin  number  of  5  and  an  acidity 
of  0.85  per  cent.     The  maximum  sugar  ratio  for  this  juice  is  1^. 

The  only  part  of  the  .roselle  from  which  jelly  should  be  made  is  the 
calyx.  Leaving  the  seed  pods  in  during  cooking  does  not  affect 
the  flavor. 

.   The  poha  usually  contains  a  very  dense,  long-fibered  pectin.     The 
proportion  of  pectin  is  quite  low,  but  the  acidity  is  usually  high. 


24  BULLETIN  47,   HAW  An  EXPERIMENT  STATION. 

The  best  proportion  of  water  to  pohas  is  0.15  pound  to  1  pound  of 
fruit.  This  produces  a  juice  with  a  pectin  number  of  3J  and  acidity 
of  1.45  per  cent.     The  maximum  sugar  ratio  of  this  juice  is  1J. 

Jellies  of  good  consistency  and  flavor  were  obtained  with  the  fol- 
lowing variations  in  sugar,  pectin,  and  acid  content  of  the  jelly: 
Guava  jelly  between  0.48  and  0.7  per  cent  pectin,  0.6  and  0.75  per 
cent  acid,  and  60  and  70  per  cent  sugar;  grape  jelly,  0.56  (minimum) 
pectin,  between  0.7  and  0.85  per  cent  acid,  and  60  and  67  per  cent 
sugar;  roselle  jelly,  0.63  (minimum)  pectin,  between  0.5  and  0.7  per 
cent  acid,  and  63  and  72  per  cent  sugar;  poha  jelly,  0.35  (minimum) 
pectin,  between  0.8  and  1.0  per  cent  acid,  and  70  and  75  per  cent 
sugar. 

The  consistency  of  a  jelly  is  determined  to  a  large  extent  by  the 
physical  properties  of  its  pectin.  A  gelatinous,  short-fibered  pectin 
produces  a  weak,  tender  jelly,  such  as  is  obtained  from  the  grape  or 
roselle,  while  a  dense,  long-fibered  pectin  produces  a  dense,  strong- 
textured  jelly,  such  as  is  obtained  from  the  guava  or  poha. 

o 


S*p99$ 


